The problem of effectively and economically disposing of hazardous waste materials is becoming increasingly more acute. Chemicals such as polychlorinated biphenyls (PCB's) are by-products of our advanced technology which create an enormous health risk. Such chemicals are unusually stable when exposed to the environment, and when ingested by an animal, are neither broken down by the normal metabolic pathways nor excreted. Thus, they tend to become concentrated in the food chain and can exert their toxic effects for generations.
The stability of such toxic compounds as PCB's makes ordinary disposal techniques unsuitable. Disposal in landfills or sealed containers merely reserves the health risk for future generations. The only effective safe disposal of such compounds is one which decomposes the compound to nontoxic fragments or its basic forms.
Such decomposition is ordinarily accomplished by incineration at high temperatures. Typically, temperatures of 2000 to 3000 degrees centigrade are used with dwell times in the incinerator being consistent with the degree of destruction required for the particular waste material being incinerated. In addition, in conventional incinerators, fuel oil or natural gas is mixed with the material being incinerated to achieve or maintain the minimum required temperature for decomposition. This means that a temperature limitation problem arises. The maximum temperature of the material to be incinerated will be limited to the temperature of the furnace flame, and the result is that a long dwell time in the furnace may be required to achieve decomposition. See e.g. U.S. Pat. No. 4,481,891.
An alternative to the conventional incinerator is a system which utilizes a thermal arc plasma. See U.S. Pat. Nos. 4,509,434; 4,582,004 and 4,644,877. Because temperatures of more than 10,000 degrees centigrade are possible with plasmas, the dwell time can be substantially reduced. Such a system is presently being employed commercially by Westinghouse Plasma Systems in their Pyroplasma waste destruction unit. The Pyroplasma unit occupies the space of a large semi-trailer truck. It is able to process up to 3 gallons of certain types of liquid hazardous waste per minute with an electric power load of 750 kw. The purchase price of the unit is considerable and, as can be appreciated, the operating expense is not insubstantial.
Another type of plasma incinerator is seen in U.S. Pat. No. 3,818,845. In this case, a glow-discharge plasma, which is normally at lower pressure than the thermal arc plasma, is maintained by a low frequency r.f. potential applied around a reactor vessel. While the electrical power requirements of such a system are lower than the thermal arc plasma system, the throughput of the glow-discharge system may not be as great.
The present invention also utilizes a glow-discharge plasma. However, in this case a cyclotron resonance plasma is produced. In such a plasma, particles are not only ionized but are also caused to accelerate. Decomposition to basic forms of hazardous waste material such as PCB's is thus accomplished not only by high temperature, but also by bombardment by these accelerated particles which ionize and atomize the waste molecules. It is thus an object of this invention to decompose to basic forms hazardous waste material in a manner which is both more efficient and more economical than heretofore possible.
The cyclotron resonance plasma is produced by the resonance that occurs when the frequency of the electromagnetic radiation is set equal to that of the gyration of electrons or other charged particles in a magnetic field. It has the capability of selecting particular materials, based on their charge-to-mass ratio, for separate treatment. Its primary application, here, is the decomposition of hazardous waste materials by this process.
The hazardous waste material may be either a solid, liquid or gas. If it is a solid or liquid, either thermal heaters, direct combustion or electromagnetic heating can be used to vaporize the material. This vaporized material, together with a "feed" gas is injected into a reaction chamber. A set of magnetic field coils surrounds the chamber and is energized to provide a base magnetic field for the cyclotron resonance.
Electromagnetic radiation is fed into the chamber by means of hollow waveguides, ridged waveguides, or other suitable coupling devices. The frequency of the radiation is adjusted to match the desired resonance condition which is: EQU F.sub.res =(1/2.pi.)(qB/m) hertz
Where q is the charge of the electron or ion, B is the strength of the magnetic field and m is the mass of the electron or ion. The strength of the electromagnetic radiation is adjusted so that the gases flowing through the chamber are ionized, forming a plasma. During the reaction, the charged particles collide with neutral particles, providing both ionization and fragmentation (the breaking up of high-mass molecules into lower mass fragments). When electromagnetic radiation is applied at the ion cyclotron resonance frequency for a particular charge-to-mass ratio, ions of this ratio are accelerated outward and collide with other particles in the plasma. This can result in further fragmenting of these ions or other particles or the ions will be selectively expelled or collected at the outer boundaries of the reactor.
Monitoring devices are used to determine the extent of the desired treatment of the flow gas. Examples of such monitoring devices may be mass spectrometers, optical spectrometers or laser-induced fluorescence devices. A system of automatic shut-off valves are connected in the output line to keep unprocessed gas from the atmosphere.